Tailoring Cluster Configurations Enables Tunable Broadband Luminescence in Glass

Tunable light sources are highly anticipated for a variety of advanced applications. Precipitation of optically active centers in glass is an effective way to tune the optical properties of luminescent materials. However, it is challenging to obtain such stable precipitates at the subnanoscale in glass to obtain broad-band luminescence. Here, we show that stable subnanometric (<2 nm) tellurium (Te) clusters in TeO2-doped glasses can be generated directly by melt quenching. Density functional theory (DFT) was applied to calculate the energy levels of Ten clusters and thereby predict the luminescent behavior. On the basis of the DFT calculations, we designed a series of Te-doped germanate glass compositions which display broad-band luminescence. We propose the topological cage concept to tailor the cluster configuration and thus achieve tunable luminescence over a wide range of wavelengths from 600 to 1500 nm. Furthermore, the mechanism of Te luminescence in glasses is clarified in terms of cluster configurations defined by topological cages.